Communication system



Jan. 6, 1942. R. H. CAMPBELL I COMMUNICATION SYSTEM Filed June 28, 1940- station. I

"ingla visual signal-upon Patent ed Jan. 6', 1942 V 7 15mm 11. assisted-mile, 1 m, Mina; its

' s me 7 The present invention pertains to intercom;

Webster Electric: comm. poration of V sp u qgio sun zs, s oes l l 3e3 l muiiication 'systemsQfand more {particularly intercommu icating systems ofthe mudspeskms" typejemployingjampliflers; and has for its prif mary object the provisio i'oifa .systemirenderirig it less possible to connect amplifiers IITBGHESF' whereby undesirable" overloading and 'objectioh-f able noises-otherwise resulting are avoided; r

,In loudspeaking intercommunicatihg systems "or the type" comprisirigi a-"plurality of stations I each including an amplirier; a translatihfde-j 'vice'utilizable both as'amicropho'ne and-a receiver; a communicatioii coiitrol switch normal tion 4 applications Serial N08342.8 35 and"342,836'fi1ed i re disclosed cliiimed'iii co-pending I conterhporafieou'sly'herewith. The 'firs't oi these also disclosesarid circuit. arrangements y for"controllingthe'operativeriess oftheamplifler.

Other objects arid advantages or thoprese t invention will become apparent tom-the ensu-" ingdescripticiifinthe course ot'which reference is made to the accompa ying drawirlig, the single feature ,of which schematically represents a pre- 1 ieri'edeliibodiriiiit ofr'the invention! l r that the illustrated iiitercommuhication system ly' connecting the device "to an 'interstatiozi cir cuit for the reception of-call's'lfromother stations arid' operableiinto positionsto connect the inter-Q v station' circuitto the input of the amplifier and Q the device to the "output of the amplifier, and vice versafitis" possible to corir'i'ec't theoutput'oi onel 2 der (me commiorarcomndumcationr direction amplifier to the input of another amplifier.

s lt sl may aptly e e f we. pliflcation, that'is;two amplifiers.in'series are 5 used instead oi one forwhich the systemfis dc- I signed; This double amplification results in Va 7 very undesirable foverloadir'ig or the amplifier 1 whose input is comfiectedfto *thekoutput of;-jthe 7 other because of the "eiicessive voltagesuppliedi to the 'input or the'arnplifier; whichi's-normallv? excited only by the low voltage derived from the translating device, 'ordinarily hiloudspalrer oi the permanehtmagnet type, when'uunzedss v a microphone. In addition,"the-result' is the'pro se 5 h? 9M 1 It is an object of the present ihveiitiod to 1A further object =61 the invention is to provide a circuit controlling. means-jIor mOdiIy'iHE "as I provide-anew and improved systembi thetype described above wherein, upon selection or a busy station by ar otherfstationpthe circuitjconr' ecthe circuit of the amplifier and also for provid} A se n his? station,

Another object provide a system wherein the circuitmodiiyingmeans at a selected and not busy stationdscohtrolled to prevent the operator-at thecalled :stationirom utilizing the amplifier thereat; where stations are in communicatiomwith' each other.-

Other" circuit arrangements for giving; indica-l tion of the operative condition of a selectedsts) 55' oi the present irivehtio iis 60' smemmgmqmusy-wun thezco'mmunication'di liy"double"ampliflcationfis prevented'when two Vrectio'n"cqiitrol lswitch llgif 'lfhe'B supply "cir-" 7' cuit'to the amplifier is comple'ted when the comvmimi'cation direction control vswitch 'is foperated tcconjditionthe .stalioii foreither'talking or 118? is'ofthe ioudspeaking 'type' whereiri Jcomn'iunica' tion is carried oii alternately i ifi opposite direci v ,tions between a 'pluralitv-ot master stations under' the control oi' ma imsllyoperablecpmuiuni cation I direction control switches and wherein.

communication may be jcarr'ied {cri between a master; station; and one or more substations uncontrol s'witch atthemastergstationi The master stat ons are indicated prc'ividedv with jtranslatig'g devices capablei'ot be- F both {as niicrophonesg loudspeakers; s'uch ,as tlvie loudspeakers?! to ih' a f elusive, which may I be iot- -the *welbkhbwn Jpn 30 manent' -niagnet type. *The hiaster'stations l; i and 3 are provided withempliflers l5,"l6;.ensii1,f

"communication direction, control switches 18, ['9' arid-:20; and "station selector jswitches '21 '22 1am! 23.11.11 respectively; it e Thefll p m y be-of anyjwell-knoiwn con-1 struction; and from ;.-the itmay be seen that only the amplifier zll atstatioz [has been illustratedin detail. g'i'he amplifler comprisesan tions at the selecting station are so" modifled' that" put transformerclllaxid an output transformer the operator thereat isfprevex tedjirom either. =1istening or t'alkinfthroiikhthe amplifier" the'reat.'

"interconnected by two stages of amplification; Power is supplled'to=the amplifler from a siiit-.,-

' able source'foi vultex natins currentthrough "a transformer .ILandZin par't thrOlmh a rectifier 7 '21. 'The supply of-rectifled current itheJBrfsup ply) is 1 directed to the amplifier "through con;

nected" "directly to a common conductor 30 of the'ampliflergwhichis grounded asrindica'ted tening, and the power is. cut off when the station is in idle condition.

The amplifier is conditioned to be ready for instantaneous use whenever the communication direction control switch is operated simultaneously to condition the, station for talking or listening and to complete the B supply circuit by reason of the fact that the cathode heaters 34 of the two tubes ofthe amplifier are continuously supplied with heating current from a secondary winding 38 and transformer 28, the mid point of which is connected to the common ground conductor 30 by the conductor 38.

The communication direction control switch I8 is a manually operable multi-pole three-position switch; In a first position (the normal and the up and idle position), the loudspeaker II is connected directly to a communication circuit comprising conductors 40 and 42 for the reception of calls from other stations provided with ampli-' fiers; that is, some other master station. In a second position (the intermediate and listening position) the loudspeaker is connected to the output and the communication circuit to the input of the amplifier. In a third position (the down and talking position, from which the switch is biased by a spring 43 into its intermediate position upon release) the loudspeaker is connected to the input and the communication circuit to the output of the amplifier. a

The connection of the loudspeaker to the communication circuit. in the idle-position of. the communicationdirection control switch, in which the switch I8 at stat-ion I is illustrated, is as follows: From conductor40 through switch blade 44 and conductor 48 and from conductor '42 through switch blade 48 and conductor 50., In passing, it may be noted that in the idle position of the communication control switch, the.

B supply to the amplifier isdisconnected by reason of the fact that the circuit through .con- .ductor 28 is interrupted by switch blade 32.

The connection of the loudspeaker to the output and the communication circuit to the input of the amplifier in the intermediate position or the communication direction control switch (in which position switches Hand 20 at stations 2 and 3 are illustrated) is efiected in the following manner: The loudspeaker II is connected to the output of the amplifier through conductor 48,

same time, resistor 12 is connected in parallel with loudspeaker I I, in order to maintain substantially constant the impedance of the receiving circuit through a conductor 14 connected to con ductor 50 and resistor 58, conductor I8 and switch blade 18. The connection of the communication circuit to the input of the amplifier is efiected through switch blade 44, conductor 80, normally: closed switch 82, controlled by a normallyenergized solenoid 84 forming one of the important features of the present invention, and the operation of which will be described in greater detail hereinafter, and'conductor 86 to one terminal. of the primary winding 88 of input transformer 24 and from the other terminal of this primary winding to conductor 42 through conductor 80 and switch blade 48.]

The connection of the loudspeaker to the input and the communication circuit to the output of the amplifier in the third position of the communication direction control switch is effected in the following manner: The loudspeaker is connected to the input through conductor 46, switch blades 54, 52, conductor 80, the normally closed switch 82, and conductor 86, leading to one terminal of the primary winding 88 and from thence back to the other terminal oi. the loudspeaker through conductor 80,-switch blades I0, 68, and conductor 50. The communication circuit is connected to the output of the amplifier through switch blade 44, branch conductor 02, and conductor 60, leading to one terminal of the secondary winding 82 and from thence to the other communication conductor 42 through conductor 64, branch conductor 84, and switch blade respectively to the output conductors 84 and.60,.

so as to short-circuit the output when the com munication direction control switch is operated from its listen to itstalk position, or vice versa.

An important feature of the present invention is the provision of means preventing double amplification whenv the system is operated properly and decreasing the possibility of double amplification when the system is improperly operated. In the instant embodiment, this means comprises circuit modifying means, namely, the previously-referred-to solenoid 84. This solenoid is normally energized, that is, when the communication control switch is in its idle position, from the rectifier through conductor I00, resistors I02 and I04 connected in parallel by conductors I 08, I08, IIO .and switch blade II 2 connecting conductor IIO toconductor I08 and conductor H4. Solenoid 84 is shunted bya condenser H8 and connected. to ground through a conductor 1 The solenoid 84, when energized, as it is under normal conditions, not only closes switch 82,

but also closes switch I20 to connect a combined pilot and busysignal light I 22 to a portion of the secondary winding 38 associated with transformer 25 througha circuit including conductor I24 andground connection I28; r

The resistors I02 and I04 are so proportioned withrespectto the resistance of solenoid 84 that, when the communication control switch is operated to its intermediate or lowermost-positions, at which time conductor H0 is grounded by switch blade H2 through the groundconnection I28, the solenoid 84 is maintained energized.

Good. results have been obtained by using a.

40 and 42. ,These resistors. have resistances of about500 ohms-each. V

The above-described arrangement is such that if the operator at station I selects a station that is not busy, then'the solenoid 84 remains energized so that the circuit to the input of the amplifier is completed by. switch 82. However, if the. operator at station I selects a busy station,

with the communication control switch at station and by conductor I12 toground. The solenoid I in its normal positiomfthen the solenoid 86 is rendered inefiective'to maintain switch 82 in its closed position, and as a result the switch 82 is opened, rendering it impossible forthe operator at station 'I effectively to utilize the amplifier I5. Thus, it is impossible for thejoperator at station-I to connect amplifier I in cir'cuitwithf a busy station so as to create what has-been termed double amplification.

A further advantage of the described arrangestation tries to listen to ment is that if another is also shunted by a condenser I". The solenoid what is going on at station l, then the solenoid 84 is de-energized and the pilot light: I22 is extinguished to indicate this. The above-described] advantages will become more apparent froma detailed description of the operation, appearing hereinafter 'following a description. of the other stations in the system. The selector switch switches individual to station I, as for instance the two indicated by reference character I34,

2 I 1 at station I includes which are.termed the station number I switches and which are ordinarily maintained in closed as having thesame number of switches as selector switch 2|, and closed in orderto connect I for the reception 'ofcallsi'rom other stations.

the switch blades I36 thereof fare The selector'switch 23'at station 3, not illus beenshown as including only trated in full, has

position in order that other stations may communicate with station I." E'achoi the master; as many pairs of switches f the system, so that each station 2 to' the system shunted by a a 220.; The i solenoid is =no'rmally energized, =and= the amplifier input; circuit" is the two pairs of switches" I38 and I", the former} i of which may be considered as'being the switches 1 associated with station ,3.

The loudspeaker Mat station' is connectei'l directly by conductors I42 to one pair of inter-- station conductors so that it maybe placedin] of the master stations whenever the proper selector switches arebper:

communication with any ated at the master'stations. a The apparatus at stations 2 identically with that at station aud tor this reasonit is not deemed necessary to describe the various "circuit connections in detail. Itmay befnot'ed, however, that *the' communication:

switches at stations 2 and 3 have been illustrated in their intermediate positions, -as distinguished from thecommunication controlswitch as sta tion I, which is; illustrated inits normal orup' permost position. I'hesignallingcircuit, howthe resistors I48 and I56 and from between them there extends a conductor I52 to switch blade I54 illustrated in the listen position wherein, and

in the talk position, it completes a'circuitto ground through grounding connection I56. The switch is operable in its uppermost position to complete a connection and 8correspon'ds'f .5.- ever, to which the present invention'primarily' described in ord'erthat a better between conductor I52 and from affisuitable alternating "current source" to be connected to a by conductor I64;

' The communication circuit-at station 3 comprises the conductors I86 and 188- across which are connected in seriesgthe resistors-I86 and 162'," from between which; leads a, conductor IN {to switch blade I86. 'In' the-indicated position oi. the switchjblade and in the talk position,'it com pletes the circuit to lug connection I98; upwardly to complete a circuit between conductor ground-through the ground I84 and a conductor I88 andco'nductor 20Il to connect in parallel the resistors 2B2-Iand 26l'.,' I I The'adjacent ends of resistors202'and 266 are connected by a conductor 266 to 1 a sourceffoi' power (potshown) whichmay be, as at station I, the rectifier associatedv with the amplifier.

The circuit modifying solenoid at station Sis in?- dicated by reference character 208, one terminal of which is connected 7 by conductor .2 I II to icon ductor I98 and theother- ;terminal' offwhich is grounded by a "conductor 2 I 2. The solenoid 'i's 2I8, the first of which controls the amplifier input when) so energized,

completed and the light 'connected gto a: suitable" 222; and thein] detail} it is contemplated that eachorfthe 4 amplifiers will norm'ally be supplied 'with 1 power "through'thetransforiners andthe communicationcontrol switches-'- will be in their uppermost I positions, such as that at stationil; Asa result, the solenoid; windings will normally- -be' ener-a gized andthe electriclights supplied with en'ergy,

whereby these lights willact as-pilot iightsjin addition to acting'assig na1ling devices, and the amplifier input circuits; will be completed; The

amplifiersare normally inoperative, but areconditioned tor'instanta'neous operation by reason "of the fact that thec'athode heaters are normally' supplied with energy,'but the B supply conductor I58 and conductor I60 "to connect in parallel resistors I62 and I64. Energyfrom"thef rectifier (not shown) associatedwith amplifier I6 is supplied through a conductor I66 to the circuit modifying solenoid at station 2, indicated by reference character I68; The solenoid is connected by conductor I'III to conductor I58 I .sistors m and I32 at statlo'n 'l is ungroun'ded;

is' cut off by thefswitches 32 associated with the various communication. control switches. The

station selector switches individual to the re-.

spectivestations are closed so'as to conditionthe stations for the reception of, calls from other stations; '2 I.

In the description or the operation, it is assumedthat-statioa I is not busy, and that the communication;controlswitch I8 thereat is in its idle position and ."that station 2 desires to communicate therewith. 1 Then, with the communication control switch III :at station 2 in its idle position, the operator at sta'tion2 closes the up perrnost pair of switches ofselector switch 22 to connect the communication circuits 6; 42 and 4,146. "Inasmuch as the point between rethe solenoids "at stations I and 2 remain-"energized, "thus giving an indication to the operator The switch bl'adeis op rablecondenser 2| 6 The solenoid has j associatedwith it a pair of switches 2I'6 and circuit and the latter- .01" which controls a" circuit to the cdmbin'dfpilot and signal light at station. 2 that the selected station is free to receive a call. The operator at station 2 may then operate the communication control switch I8 thereat to its listen or talk position, at which time switch blade I 54 connects to ground the point between resistors I48 and I50. The result erates the communication control switch to its talk position, then the operator at station 2 can talk to the operator atstation I. At thistime the loudspeaker I2 at station 2 is connected to the input at amplifier I6 and the loudspeaker II at station I is connected to the output of the amplifier I5. Thereafter communication may be carried on between the two stations by the operator at station 2 manipulating the switch I8 tliere at between its middle and lowermost positions.

Ii the operator at station 3 should now select either station I or station 2 with the communication control switch 20 thereat in its normal position, the solenoid 208,.at that station is deenergized to indicate to the operator that station I or 2, which ever is selected, is busy, and likewise the input circuit of amplifier I1 is broken, so as to prevent double amplification. The de-energization oi solenoid 208 results from the .fact that with switch blade I88 in its uppermost position, the solenoid 208 is grounded through the interstation circuit and through switch blade I54 at station 2.

It should be noted that the amplifier-Ii at station 2 remains operative when the solenoid I88 is initially energized and the communication control switch then operated to its listen or talk position. The solenoid is maintained energized by reason of the fact that even though conductor I82 is grounded, the ground circuit= extends through resistor I84, so that only a portion of the current supplied to thesolenoid is shunted therefrom.

From the above-described mode of operation, it may be seen that the present invention provides an arrangement whereby double amplification is prevented when two stations are in communication witheach other. Double amplification is also prevented when a third station properly selects either of the two stations in communication. Thus, if the selection 01 one of two busy stations is made with the communication control switch at the third'station in its proper position, it is impossible for the selecting. station either to talk or listen through the amplifier thereat, although the operator at station 2, taking a specific instance, can listen to the conversation between stations I and 2 through the loudspeaker I3 with the communication control'switch in its uppermost or idle position.

The mode of operation of the system is sub stantially the same when station I is in communication with the substation 4. At this time conductor H at station I is connected to ground by switch blade II2. Solenoid 84 remains energized, but if station} or 3 should now select station I, then the solenoid 208 .thereat is grounded through the previously-mentioned tions. If this mode of operation be followed,

then the solenoids at the two stations are alternately nergized and de-energized, so that the amplifiers at thetwo stations are alternately rendered operative. However, as in the first-described mode of, operation, it a third :station should select either of the two stations communicating with each other, the solenoid at the first station is de-energized to give the operator at the third station an indication that the selected station is busy, and likewise to prevent the operator at the third station from effectively utilizing the amplifier thereat whereby double amplification is prevented.

It is to be noted that while only a comparatively few stations have been shown in each of the embodiments illustrated, it shoulg be understood that the number of stations may' be multiplied to any extent desired. Although the invention has been disclosed with specific de-- tails of preferred embodiments thereof, it should be understood that such details are not intended to be limitative of the invention except in so far as set forth in the accompanying claims.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent of the United States is:

1. In a multiple station intercommunicating system, the combination including, signal means at each station, current responsive means nor,- mally occupying a predetermined position controlling the signal means at each station, 'an emplifler at each station, a communication control switch at eachstation associated withthe amplifler thereat, an amplifier circuit controlled by said switch, and switch means in said circuit operable by said current responsive means. 7

2. In a multiple station intercommunicating system, the combination including, a'communb cation control switch at each station, an ampliher at each station, an amplifier input circuit controlled by said. switch, switch means in said input circuit, and current responsive means at each station normally occupying a predetermined position for controlling said switch means.

3. In a multiple station intercommunicating system, the combination including, means .in-.

'cluding a switch and an amplifier having input and output connections controlled thereby at each station for establishing communication'circuits between stations, switch means'in said input connection to the amplifier, and current responsive means for controlling said last-mentioned switch means. V

4. In a multiple station intercommunicating system, the combination including, means including a switch and an amplifier having input and output connections controlled thereby at each station for establishing communication circuits between stations, switch means normally occupying a circuit making position in said inbut connection to the amplifier, and current responsive means operable in response to selection of a busy station for operating said second-men.- tionod switch to a circuit-breaking position.

5. Ina multiple station intercommunicating system, the combination including, a translating device at each station. utilizable both as a microphone and a receiver, an amplifier at each of the communication direction control switch to its second or third positions the solenoid at the called station is grounded and the switch controlled thereby operated to break the input to the amplifier at the called station.

M 11. In a multiple station intercommunicating system, including in combination, a translating device at each station utilizable both as a microphone and a receiver, an amplifier having input and output connections, an interstation circuit, a selector switch for connecting the output circuit to selected remote stations, a multi-pole communication direction control switch normally occupying a position wherein the interstation circuit is connected to the translating device, and operable to a second position wherein the interstation circuit and device are connected to the input and output of the amplifier, respectively, and to a third position wherein the connections of the interstation circuit and device to the amplifier are reversed, a switch in the input circuit or the amplifier, a solenoid controlling said switch, a source of power for said solenoid, a switch operable by said communication control switch and circuits controlled thereby for connecting said solenoid to its source of power and to the interstation circuit in the normal position of said communication control switch and for connecting the interstation circuit to ground in switch controlled thereby operated to break the amplifier input circuit, and whereby when one station selects astation that is not busy and communicates therewith by operation of the communication direction control switch to its second or third positions the solenoid at the called station is grounded and the switch controlled thereby operatedto break the input circuit to the amplifier at the called station.

12. In a multiple station intercommunicating system, the combination including, an amplifier at each station having input and output connections, an interstation circuit leading from each station, voice receiving and'transmitting means at each station, a communication control switch and circuits controlled thereby for controlling the connections of the amplifienrvoice receiving and transmitting means and interstation circuit, said switch normally conditioning the station for munication control switch for connecting said device to the input and said interstation circuit to the output of the amplifier, or .vice versa, in-

I cluding in combination a switch in the amplifier input circuit, a solenoid controlling said lastreception of calls from other stations, normally closed switch means in the amplifier input circuit, current responsive means for controlling said switch means, and means associated with communication control switch for operating said current responsive means to open said normally closed switch when said station is selected for communication by another station.

. 13. A unit for use in a multiple station intercommunicating system, including in combination, signal means, current responsive means normally occupying a predetermined position controlling the signal means, an amplifier, a communication control switch, an amplifier input circuit controlled by said switch, and switch means in said input circuit operable by said cur rent responsive means. 2

14. A unit-foruse in a multiple station intercommunicating system, including in combination, a communication control switch, an amplifier, an amplifier input circuit controlled by said switch,

normally closed switch means in said input cirmentioned switch, and means responsive to the condition of a selected station for controlling the energization of said solenoid.

16. A unit for use in a multiple station intercommunicating system of the type wherein each station is provided with a translating device utilizable both as a microphone and a receiver, an amplifier having input and output connections, a source of B supply, an interstation circuit, a selector switch for connecting the interstation circuit to selected remote stations, and a multi-pole communication direction control switch normally occupying a position wherein the "B" supply to the amplifier is disconnected and the interstation circuit is connected to the translating device, and operable to a second position wherein the 3" supply is connected to the amplifier and the interstation circuit and device are connected to the input and output of the amplifier, respectively, and to a'third position wherein the connections-of the interstation circuit and device to the amplifier are reversed, including in combination, a pair of resistors of relatively low resistance connected in a series across the interstation circuit, a switch in the input circuit of the amplifier, a solenoid controlling said switch, said solenoid being connected to a source oi power through arelatively high resistance resistor, a second high resistance resistor connected between said source of power and a point between said two first-mentioned resistors, a switch connected between saidtwo first-mentioned resistors and operable by said communication control switch for connecting said first-mentioned high resistance resistor in parallel with the second-mentioned high resistance resistor in a normal position of the communicating control switch, and for connecting the point between said series connected resistors to ground in the second and third positions oi said communication control switch, whereby when one station selects a busy station with the communication control switch at .the one in its normal position, the solenoid at said one station is grounded and the switch controlled thereby operated to break the amplifier input circuit, and whereby when said one station selects a station that is not busy, and communicates therewith by operation of the communication direction control switch to its second or third position, the solenoid at the selected station is grounded and operates the switch controlled thereby to break the input circuit to the amplifier at the selected connections oi the amplifier, voice receiving and transmitting means, interstation circuit, and

2,2eo,14s 7Q wherein the control switch normal conditions the station for reception of calls from other stations,

- including in combination, normally closed switch means in the amplifier input circuit, current re- 7 sponsivemeans for controlling said means, and means associated with said communication controi switch for grounding said current responsive means through'the interstation circuit to open said normally closed switch when said station is seiected'for communication by anotherstation.

18; A unit according to ciaim 17, wherein the 1 current responsive means operates signal means when grounded.

r RICHARD H. CAMPBELL-J 

